Spatial variation in estimation of shear key forces in segmented immersed tunnels
C.M.P 't Hart 1, 2, O. Morales-Nápoles 1, S.N. Jonkman 1
1 Delft University of Technology, Civil Engineering and Geosciences, Hydraulic Engineering, Delft, the Netherlands
2 Royal HaskoningDHV, TEC, the Netherlands
Immersed tunnels are positive buoyant structures during installation and negative buoyant after installation. A tunnel is composed of sequential immersed elements that are coupled to each other in joints. Tunnel elements consist of segments which are compressed to each other by longitudinal post-tensioning. After immersion the tunnel is supported by the seabed and the longitudinal post-tension is cut at the joints between segments. Therefore, the structure is a segmented lining which is sensitive for settlements due to non-uniform circumstances over the length of the tunnel. An uneven response of the bedding underneath the tunnel introduces shear forces in joints of an immersed tunnel. Because immersed tunnels need to be buoyant during installation, they have limitations on weight and geometry, the size and therefore the capacity of these shear keys is limited because the height of the tunnel, as shear keys are applied in the walls of the tunnel. The foundation response is influenced by many factors related to subsoil but also to construction and dredging tolerances. The shear forces were derived as a function of different covariance lengths for subsoil stiffness and dredging tolerances for different tunnel layouts.
Key words: Immersed tunnels, bedding, random fields, covariance length